This invention relates to the polymerization of olefins by the coordinate complex method, often termed the Ziegler-Natta method after the names of the two workers who contributed so much to its practical development and theoretical basis. More particularly, this invention relates to novel, activated supports for the transition metal catalytic component.
About 30 years ago the original Ziegler-Natta catalysts were heterogeneous slurries formed in place when solutions of organometallic cocatalysts, preferably taken from the compounds of metals of Groups IA, IIA, and IIIA of the periodic table, were added to solutions of transitional metal catalysts, preferably taken from compounds of metals of Groups IIIB, IVB, and VB of the periodic table. These catalytic systems by today's standards did not have high activity in terms of grams polyolefins produced per gram catalyst component. Nor, when propylene or other monomers capable of giving polymers with tacticity were employed, did these early catalytic systems provide polymer with high isotactic index. Also, the particle size distribution of the polyolefin was too broad, leading to an undesirable fraction of "fines", particles less than about 100-180 .mu.m.
More recently, high activity, high isotactic index, and enhanced particle size have been achieved by employing catalyst supports on which catalytic transition metals have been dispersed. It has been theorized that the concentration of active polymerization centers is as much as 50 percent higher on supported catalysts than unsupported catalyst systems. These developments are discussed in the Kirk-Othmer "Encyclopedia of Chemical Technology", third edition, vol. 16, pp. 453-469 in an article entitled Olefin Polymers (Polypropylene) and in Angewandt Makromolekulare Chemie, 94, 63-89 (1981). One support which has gained favor in technical circles is magnesium halide, particularly in an activated condition. The preferred method for activating catalyst support such as magnesium halide is dry milling, as disclosed in British Pat. No. 1,335,887.
Dry milling suffers from many practical defects. Among these are long milling regimes, losses of support by "hold-up" in the milling equipment, excessive handling, the cost of milling energy, and a wide dispersion of the particle size of the milled products leading to excessively broad particle size distribution of the polyolefin. It would be advantageous to have the high catalytic activity of a supported catalyst, the high isotacticity of polymers capable of such (e.g., polypropylene) and a decreased proportion of "fines" without the necessity of a milling or grinding step. This is achieved by use of the present invention.
In European patent application 18,738, Example 4 discloses a process for preparing a titanium catalyst wherein magnesium chloride (MgCl.sub.2), decane, and 2-ethylhexanol were heated at 130.degree. C. for two hours to form "a uniform solution". Then ethyl benzoate was added, the solution added to neat titanium tetrachloride (TiCl.sub.4) at 0.degree. C., the mixture heated, and more ethyl benzoate added at 80.degree. C. The solid which formed upon two hours heating at 80.degree. C. was collected by filtration, and treated in TiCl.sub.4 at 90.degree. C. for another two hours.
Japanese patent application No. 80/135,103 (C.A. 94: 84852f) discloses a process for preparing a titanium catalyst wherein MgCl.sub.2 dispersed in a hydrocarbon containing an alcohol and a siloxane are heated above the melting point of MgCl.sub.2 (sic), actually the complex of MgCl.sub.2 with the alcohol, and quenched at about -10.degree. C. to form a solid. This solid is then treated at 0.degree. C. with ethyl benzoate and TiCl.sub.4, separately, treated twice at 100.degree. C. with TiCl.sub.4, separated, washed, and dried.
U.S. Pat. No. 4,294,721 discloses a process wherein a magnesium dihalide is treated with one active-hydrogen electron donor (e.g., an alcohol) and a non-active-hydrogen electron donor (e.g., an ester), dried to a solid, treated with TiCl.sub.4, and dried to form a catalyst component.
U.S. Pat. No. 4,328,328 describes a polymerization process wherein without a support three, soluble, liquid streams are introduced into a polymerization reactor to form a catalytic system in situ. The three, liquid components are a liquid MgCl.sub.2.ROH complex, a liquid transition metal compound (e.g., titanium tetrabutoxide), and a liquid organoaluminum compound.
U.S. Pat. No. 4,083,802 discloses a process for preparing a supported polymerization catalyst wherein magnesium halide is caused to react with silicon tetrachloride in the presence of an alcohol or phenol to form the support. The carrier supports a titanium or vanadium catalyst.
U.S. Pat. No. 4,330,649 discloses polymerization of olefin utilizing a supported titanium catalyst prepared by dissolving magnesium dihalide in an alcohol and a hydrocarbon, adding it to a liquid titanium compound and an electron donor having no active hydrogen atoms, heating to form a solid, and retreatment of the solid with the electron donor and titanium compound again.